Wacom made such on/off digitizers --- my NCR-3125 had one --- the "signature" pen from it would work on my Wacom ArtZ (w/o pressure), but the pressure-sensitive pen from the ArtZ would not work on the NCR.
Similarly, the FinePoint digitizer used on the Fujitsu Stylistic ST-1200 and ST-2300 as well as on the Compaq TC-1000 was on/off only.
Anyway, the units have started to show up in the wild:
https://old.reddit.com/r/kindle/comm...one_day_early/
so we should have some real information on stylus compatibility and pressure sensitivity soon.